The present invention relates to an intake air control device and an internal combustion engine mounting an intake air control device; and, more particularly, the invention relates to a technique for improving combustion performance in an internal combustion engine and for reducing the amount of hydrocarbons (hereinafter, referred to as HC) emitted at the time of warming-up operation of the internal combustion engine.
An intake air control device for an engine is disclosed in Japanese Patent Application Laid-Open Hei 4-232353. In this intake air control device, a cold-start injector projecting inside a main intake air passage is arranged at a position near an outer peripheral portion of the throttle valve when the throttle valve is in a partially open position. However, operation of this arrangement is difficult in that most of the fuel spray, which is injected in the main intake air passage from the cold-start injector projecting inside the main intake air passage and is vaporized (atomized) and transported to each of the combustion chambers by intake air flowing in the main intake air passage, is caused to adhere onto the inner surface of the main intake air passage and to be stagnated there. Therefore, it is difficult to stably supply the vaporized fuel sufficiently to each of the combustion chambers.
Further, a cold-start fuel control system comprising a cold-start fuel injector, a heater and an idle speed control valve (hereinafter, referred to as an ISC valve) is disclosed in the specification and drawings of U.S. Pat. No. 5,482,023. In this system, a part of the air from the ISC valve (a first air flow) is merged with fuel injected from the cold-start fuel injector. For this purpose, the opening of an air flow passage from the ISC valve is arranged to have an annular shape so as to surround an outlet portion of the cold- start fuel injector. The fuel ejected from the cold-start fuel injector merges with the first air flow and just after merging enters into and passes through the inside of a cylindrical heater arranged in series downstream of the cold-start fuel injector.
In addition, an air passage for allowing part of the air from the ISC valve to flow therethrough is formed in the outside periphery of the heater, and the air flowing through this air passage (a second air flow) merges with the fuel spray, which has passed through the inside of the heater, at the outlet portion of the heater. The fuel coming out of the cold-start fuel injector is further vaporized while passing through the inside of the heater and is even further vaporized as it is mixed with the second air flow at the outlet portion of the heater. The outlet portion of the heater is in communication with the intake assembly pipe, and the fuel spray which has been highly vaporized is distributed to each of the cylinders after being discharged into the intake assembly pipe.
In the above-described system, a mixing chamber for mixing the fuel and the air inside the cylindrical heater is provided to form a kind of atomizer having a heater exit forming a fuel outlet, by arranging, from the upstream side, in order, the cold-start fuel injector, the merging point of the fuel injected from the cold-start fuel injector with the air flow and the mixing chamber constructed inside the heater. It can be considered that the atomizer is an air assist type atomizer which uses the energy of the air flow, and it is also an internal mixing type atomizer which performs air-liquid mixing by merging the fuel with the air inside the atomizer.
In the above-described system, the second air flow flows into the outer peripheral portion of the heater and is merged with the fuel spray that has passed through the inside of the heater, while flowing in the same direction to promote vaporization of the fuel spray. However, in this system, the application of the fuel spray to the intake pipe and the transportation in the intake pipe after that is not sufficiently taken into consideration.
In the above-described system, the fuel injected from the cold-start fuel injector is further vaporized by passing through the narrow and long passage formed inside the heater while contacting surfaces of the heater. However, in this system, the vaporizing efficiency of the heater is not sufficiently taken into consideration.
In the above-described system, the outlet portion of the heater is in communication with the intake assembly pipe; and, the fuel spray subjected to further vaporization is discharged into the intake assembly pipe and is then distributed to each of the cylinders. However, in this system, improvement of the distribution to each of the cylinders is not sufficiently taken into consideration.
An object of the present invention is to provide an intake air control device which is capable of reducing the amount of HC emitted at the time of warming-up operation of an internal combustion engine.
Another object of the present invention is to provide an intake air control device which is easily manufactured, and easily mounted and dismounted.
A further object of the present invention is to reduce the amount of fuel adhering onto a wall surface of the intake pipe and to reduce the amount of HC emitted at the time of warming-up operation of an internal combustion engine by improving the application of the fuel injected from a second injector to the intake pipe and the transportation of the fuel to the downstream side, the second fuel injector being additionally arranged separately from a first fuel injector arranged at a position near the cylinder of an internal combustion engine and used at starting operation of the internal combustion engine.
A still further object of the present invention is to decrease the electric energy consumed by a heater for atomizing the fuel spray by modifying the behavior of the fuel spray with regard to contact with the heater.
A further object of the present invention is to improve the uniformity of distribution of the fuel spray to each of the cylinders by modifying the method of supplying the fuel spray to the intake pipe.
The present invention is characterized by an intake air control device comprising a body having a main flow passage for supplying air to the cylinders of an internal combustion engine, a throttle valve for controlling air flow rate arranged inside the main flow passage; and a fuel injector for supplying fuel into the main flow passage, the fuel injector being fit and attached to the body. The body is formed by working a body member into a one-piece structure comprising an opening portion communicating with an outer portion of the body, with the main flow passage being on a downstream side of the throttle valve; and a mounting portion for fitting and attaching the fuel injector facing an opening plane of the opening portion.
The intake air control device further comprises a first bypass flow passage communicating with the inside of the main flow passage through the opening portion, the first bypass flow passage being branched from the main flow passage on the upstream side of the throttle valve; and a second bypass flow passage communicating with the inside of the main flow passage on the downstream side of the throttle valve and on the upstream side or the downstream side of the opening portion, the second bypass flow passage being branched from the main flow passage on the upstream side of the throttle valve.